php - finding keys in an array that match a pattern - php

Question

I have an array that looks like:
Array ( [2.5] => ABDE [4.8] => Some other value )
How would I find any key/value pair where the key matches a pattern? I will know the value of the first digit in the key,but not the second. so for example, using a prefix of "2.", I want to somehow be able to find the key "2.5" and return both the key and the value "ABDE".
I was thinking about using a regular expression with a pattern like:
$prefix = 2;
$pattern = '/'.$prefix.'\.\d/i';
and then looping through the array and checking each key. (by the way, just for demo purposes, $prefix has been hardcoded to 2, but in the real system, this is a value provided by the user's input).
I'm wondering if there's a simpler way to do this?
Thanks.

Answer 1

I think you need something like this:
$keys = array_keys($array);
$result = preg_grep($pattern, $keys);
The result will be a array that holds all the keys that match the regex. The keys can be used to retrieve the corresponding value.
Have a look at the preg_grep function.

Answer 2

you can simply loop through the array and check the keys
$array = array(...your values...);
foreach($array as $key => $value) {
if (preg_match($pattern,$key)){
// it matches
}
}
You can wrap it in a function and pass your pattern as parameter

Answer 3

Old question, but here's what I like to do:
$array = [ '2.5' => 'ABDE', '4.8' => 'Some other value' ];
preg_grep + array_keys will find all keys
$keys = preg_grep( '/^2\.\d/i', array_keys( $array ) );
You can add array_intersect_key and array_flip to extract a slice of the array that matches the pattern
$vals = array_intersect_key( $array, array_flip( preg_grep( '/^2\.\d/i', array_keys( $array ) ) ) );

Answer 4

For future programmers who encounter the same issue. Here is a more complete solution which doesn't use any loops.
$array = ['2.5'=> 'ABCDE', '2.9'=>'QWERTY'];
$keys = array_keys($array);
$matchingKeys = preg_grep('/^2\.+/', $keys);
$filteredArray = array_intersect_key($array, array_flip($matchingKeys));
print_r($filteredArray);

Answer 5

That are my ways
$data = ["path"=>"folder","filename"=>"folder/file.txt","required"=>false];
// FIRST WAY
$keys = array_keys($data);
if (!in_array("path", $keys) && !in_array("filename",$keys) && !in_array("required",$keys)) {
return myReturn(false, "Dados pendentes");
}
// SECOND WAY
$keys = implode("," array_keys($data));
if (!preg_match('/(path)|(filename)|(required)/'), $keys) {
return myReturn(false, "Dados pendentes");
}

Answer 6

To get just the part of the array with matching keys you could also write
$matching_array = array_flip(preg_grep($pattern, array_flip($your_array)));
This might just lead to problems performance-wise, if your array gets too big.

Answer 7

There's T-Regx library for regular expression in PHP, and it kas preg::grep_keys() method.
<?php
$array = [2.5 => 'ABDE', 4.8 => 'Some other value'];
preg::grep_keys("/$prefix\.\d/i", $array);